CANBERRA, Australia—The Australian Navy was investigating two objects spotted in the southern Indian Ocean, where Malaysia Airlines Flight 370 was on Monday confirmed to have gone down based on satellite data.

Addressing parliament, Australian Prime Minister Tony Abbott said earlier Monday that two objects—one gray or green circular object and the second an orange rectangular object—were spotted by an Australian military aircraft about 2,500 kilometers (1,550 miles) southwest of Perth. A warship, HMAS Success, is...